1. Field of the Invention
This invention relates generally to vehicle ride and stability control and, more particularly, to a system and method for determining the pitch, roll and heave of a vehicle.
2. Description of the Related Art
The automotive industry makes considerable effort to improve the comfort and safety of the passengers of a vehicle by monitoring and controlling in real time the ride and stability of the vehicle dynamics. One problem typically encountered in ride and stability control of a vehicle is the estimation of the vehicle's dynamic states, i.e., roll, pitch and heave rates. Direct sensing of these vehicle dynamic states during the production phase of a vehicle is typically not feasible due to high cost and packaging issues.
Existing techniques for estimating the dynamic states of a vehicle typically use suspension deflection sensors. However, measurement readings from suspension deflection sensors contain frequencies of vertical wheel motion, that is, wheel hop frequencies, along with the frequencies of vehicle body motion. To accurately estimate the vehicle dynamic states, a filter must be implemented to separate the wheel hop frequency content from the vehicle body motion in the sensor measurements.
Linear filters are typically used for the purpose of removing wheel frequency components from the measurements of suspension deflection sensors. The linear filters, however, introduce an unacceptable delay in estimating the vehicle dynamic states. As a result, existing filtering methods are in general not able to provide vehicle dynamic state estimates without significant delay.